The invention relates to a convergent-divergent nozzle for a turbofan engine of a supersonic aircraft and a method for adjusting the nozzle throat surface in a nozzle of a turbofan engine.
In a convergent-divergent nozzle having a nozzle throat surface (usually referred to as A8) and a nozzle exit surface (usually referred to as A9), it is generally desirable if the degree of expansion of the flow channel behind the nozzle throat surface, that is, the ratio of A9 to A8, can be adjusted in a desired manner for different operational states.
For this purpose, it is known to design a nozzle with a variable contour, for example as an iris/petal nozzle with a plurality of individual adjustable lamellas. Thus, it is known to provide a group of convergent lamellas and a group of divergent lamellas in a nozzle, which are respectively arranged in a circular manner. In order for the individual lamellas to be adjustable, they are provided which actuators. Such a nozzle is for example known from U.S. Pat. No. 9,464,594 B2, as well as from engines of the fighter jets McDonnell Douglas F-15, Suchoi Su-27, and Suchoi Su-34. A disadvantage of such nozzles in iris/petal design is their complex structure, a high maintenance intensity, a complex control, and a relatively high weight due to the need for a plurality of actuators. In addition, high flow losses occur at the individual lamellas.
EP 2 966 267 A1 discloses is a nozzle arrangement in which a gas turbine has separate nozzles for the bypass channel, the primary flow channel, and for a mixer. An axially displaceable trim ring is dedicated to the mixer, with its axial position altering the exit cross section of the nozzle that is assigned to the mixer.
The fighter jet Messerschmidt 262 realized an engine that comprised a nozzle with a central body that was axially adjustable for adjusting the nozzle exit surface.
There is a need to provide a nozzle of a turbofan engine that is suitable for supersonic operation, as well as a method by means of which an efficient adjustment of the nozzle throat surface and/or the nozzle exit surface is facilitated.